The present invention relates to a drying machine which comprises a housing chamber for housing a matter to be dried and which executes a drying operation of the matter to be dried in the housing chamber.
In a drying machine, an electric heater or a gas burning heater has heretofore been used as a heat source, outside air is heated by the electric heater or the burning heater to thereby form the air at high temperature, thereafter the air is blown into a housing chamber in which a matter to be dried such as clothing is housed, and the matter to be dried in the housing chamber is dried.
However, in the drying machine, since the electric heater, the gas burning heater or the like is used as a heat source, energy consumption for drying the matter to be dried increases, and there has been a problem that energy costs such as electricity and gas charges soar.
To solve the problem, a clothing drying machine has been developed which a heat pump constituted of a refrigerant circuit including a compressor, a heating coil, an expansion valve, and a cooling coil and capable of circulating a heat exchange medium is utilized. The matter to be dried is dried by high-temperature air heated by the heating coil, and humidity evaporated from the dried matter is condensed by the cooling coil, and discarded (see Japanese Patent Application Laid-Open Nos. 2001-62194 and 2003-53089).
To dry the matter to be dried in this drying machine, there are: an inner air circulation system (see Patent Documents 1 and 2) for discharging air whose heat has been changed with the radiator into a housing chamber by a blower, allowing the air passed through the housing chamber to exchange heat with the evaporator, thereafter returning the air again into the radiator, and discharging the air into the housing chamber; and an outer air introduction system (see Japanese Patent Application Laid-Open No. 11-99299) for introducing air from the outside of a drier, exchanging heat with the radiator, discharging the air into the housing chamber, allowing the air passed through the housing chamber to exchange heat with the evaporator, and discharging the air to the outside. There is also a system in which a part of an air circulation system communicates with the atmosphere (see Japanese Patent Application Laid-Open No. 10-33896).
However, in the former inner circulation system, the air discharged into the housing chamber can be at high temperature. However, a large amount of water content is contained in the air which has dried the matter to be dried especially in an initial stage of a drying operation. Therefore, all water contents cannot be recovered by the evaporator. Since humidity-containing air is sent into the housing chamber, there has occurred a problem that drying efficiency drops.
Moreover, a compressor having a large capacity has to be used for recovering the large amount of water content in the initial stage of the drying operation by the evaporator, and there has occurred a problem that power consumption increases.
On the other hand, in the latter outer air introduction system, the temperature of the air discharged into the housing chamber depends on an outside air temperature, the discharged air for use in the drying cannot be easily set at the high temperature especially when outside air is at low temperature, and there is a problem that much time is required for drying the matter to be dried. Therefore, the electric heater or the compressor having a large capacity needs to be used in the same manner as described above in order to shorten a drying time, and there occurs a problem that the power consumption increases.
Moreover, to solve both the problems, even when a part of the air circulation system communicates with the atmosphere as described above, circulating air cannot be sufficiently replaced, because outside air is introduced and discharged through one opening.